Infection with a virus may prevent the development of one form of diabetes in mice - raising hopes of treatments for humans.

The animals were starting to develop Type I diabetes, in which key cells which produce the hormone insulin are destroyed by an overactive immune system.

However, when they were given a virus called LCMV during this "prediabetic" period, the mice did not fall prey to the condition.

The Californian scientists involved say that viruses could help humans threatened by Type I diabetes.

Younger patients

Type I diabetes often affects younger patients, and involves the rapid loss of certain cells in the pancreas responsible for making insulin.

This hormone is key to the correct regulation of sugar levels in the blood, as high sugar levels can be dangerous, both in the short term and over longer periods.

Patients are often left completely dependent on regular insulin injections for life.

Type I is distinct from the more common Type II diabetes, which affects generally older people.

Other experts have noticed how the course of "autoimmune" diseases - which Type I diabetes is - appears to be altered when the patient picks up a viral infection.

Some viruses, however, are blamed for triggering such diseases.

Researchers at the La Jolla Insitute and Scripps Research Institute decided to test the effects of a particular virus, called lymphocytic choriomeningitis virus (LCMV) on the mouse equivalent of autoimmune diabetes.

Timing 'crucial'

When the virus was introduced when the mice had not yet developed a diabetic condition, the loss of these key cells was halted completely.

Writing in the Journal of Clinical Investigation, the researchers said that the arrival of a virus before the disease became apparent might be beneficial to humans.

"Viruses that do not directly destroy beta cells can enhance the course of autoimmune diabetes through several different and distinct pathways," they wrote.

However, they added that the precise timing of the infection and the area affected by the virus might be crucial to success or failure.